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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
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Posts: 1567
I have a non-inverting opamp that feeds the output to one of the ADC pins on my ATMEGA328. I read 4.5 volts on the opamp (LC6064), which has a low-offset for my needs. However, despite there being the correct voltage on the arduino, I get less than 0.5, if not lower, reading on the analogread. I probably get about 96 out of 1023.
However, when I swap the opamp with a MC3403 everything works fine.
So, this has something to do with the chip, and I am not sure what parameters on the datasheet would help me figure this out. Can anyone offer some help?
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
How would I get the time constant? I don't know how to measure the internal values. I believe I've read that the cap is about 14pF. The resistance is about 20k for a tC of 800uS. Again, this is what I've read and not measured.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
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Posts: 874
I'm not sure, but might run into this problem. Maybe three different accurate voltage sources and the time that it got read with the source voltage max, and brute-force the instantaneous voltage reading. I think a battery would probable be accurate enough, with multiable samples?
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arduino ADC and opamp issue
